Not applicable.
The very wide acceptance of sports oriented molded rubber sole footwear over the past few decades has prompted the shoe production industry to expand the involved technology to a broader range of shoe products. Appealing features of the molded soles are, for instance, their comfort, their enhanced frictional engagement with walking surfaces and their immunity from deterioration when they become wet. Comfort is established by molding the interior of the sole with lower durometer and thus softer material which is 3-dimensionally contoured to support the foot with a shaped heel cradle, arch support and toe grip. Outside portions of the molded soles then are formed with a stiffer, higher durometer value material to establish desired strength or robustness. The resultant molded sole typically will exhibit a maximum thickness of about ⅝ inch at the heel-arch region, such thickness diminishing or tapering non-uniformly toward the toe region to a thickness of about xe2x85x9c inch or less. To assemble the shoe products, for example, fashioned as slippers, it is necessary for sewing machine operators to sew a preassembled cloth upper to the molded relatively thick soles. Attachment of the upper is made at an integrally molded continuous rim extensible outwardly from either the top or bottom of the molded sole. Such sewing attachment may be carried out directly or using such fabrication procedures as xe2x80x9cstitch and turnxe2x80x9d.
Heretofore, the requisite sewing attachment procedure has posed a fabrication cost barrier for a variety of reasons. Basic ubiguitous flatbed industrial sewing machines available in essentially all factories have sewing surfaces which will be located below the necessarily elevated molded sole rim. Thus, without more, they are incapable of carrying out the sewing task. Somewhat specialized sewing machines such as cylinder or post machines are incapable of performing this necessary task inasmuch as the operator is unable to hold and align the work pieces for sewing and the stitching will be improperly positioned due to the inherent design of the machines. Further, the cost of providing the factory floor with customized sewing machines would be prohibitive both in terms of machine cost and operator training.
To produce these new shoe products at acceptable costs, it is necessary that a custom retrofit of the basic flatbed sewing machine be achieved at a practical cost level. In the latter regard, the retrofit must be carried out without altering the camming mechanisms or stroke of the machines and the machines must be easily reconvertible to their initial basic status. This alteration to the original structuring of the machines is necessary, inasmuch as the products may be produced on the production floor for relatively shorter intervals, for example, about three months. Following those intervals, then the machines are returned to fabrication of more conventional products.
Efficiencies of production also are predicated upon the type of task required of the machine operators. In this regard, the hand aligned molded sole and cloth upper must be held together and advanced through the sewing station. This generally calls for holding the entire assemblage with two hands as the bottom of the sole is slid over a flat support surface. It is necessary that the operator assert a slight downward pressure during this sliding maneuver and not be called upon to support the assemblage entirely with the hands. Lack of such full hand support not only results in relatively poor quality stitching but also induces unacceptable operator fatigue. The noted necessity of sliding the sole over a support surface also poses the inherent problem that the molded sole will have been structured to resist sliding activity.
The present invention is addressed to method and apparatus wherein a basic flatbed sewing machine design is converted for sewing through a thick workpiece such as a molded rubber sole having a sewing rim extending from either its top or bottom surface. To connect such a sole with an upper by a stitching procedure, the design facilitates the operational tasks of the sewing machine operator, permitting the holding of the two pieces to be joined with both hands and permitting the thus joined and aligned assemblage to be held down against a work surface as well as an upstanding guide surface. This arrangement achieves both accurate and desirably positioned stitching and results in less operator fatigue and substantial minimization of any opportunity for xe2x80x9ckick-outxe2x80x9d of the workpieces being joined together.
With the approach of the invention, preexisting basic sewing machines can be retrofitted very simply, for example, using a screwdriver, at relatively low cost inasmuch as the drive mechanisms of the basic machine, for example, incorporating cam actuation and the like are not altered. Correspondingly, the stroke of the machine is not altered. Thus, sewing machines with which operators are already familiar may be retrofitted for the production of footwear such as slippers or the like with relatively thick molded rubber soles and cloth uppers for a given production interval, for example, three months. Following that interval, the machines readily are converted back to their original structuring for production of a next product. As a consequence of the resultant low cost tooling for these specific products, cost of the products themselves are substantially reduced to the extent that superior products are cost competitive with preexisting inferior ones.
Successful conversion is achieved inter alia, through the utilization of a conversion feed dog assembly incorporating a conventional workpiece advancing component which performs at the original flatbed level but also includes an upstanding thread sequestering channel through which the needle of the machine passes in which, in particular, during a down stroke extending through the workpieces being sewn together avoids thread breakage by maintaining the lock-stitch forming thread loop at a size avoiding thread breakage when operationally associated with a rotating sewing hook. The cover plate is reconfigured such that it incorporates a platform-like structure with an outwardly disposed guide surface and an upwardly disposed elevated sewing surface carrying a needle receiving slot. Thus beneath or adjacent to this slot resides the needle receiving opening of the conversion feed dog thread sequestration channel. Accordingly, where the platform height corresponds with the bottom of rim to opposite side of a molded sole at its maximum thickness, the side of the sole opposite the rim may be advanced against friction by the workpiece advancing component of the feed dog while the rim is advanced at the elevated sewing surface by the top feed mechanism of the machine. To aid the operator in holding the aligned workpieces together and in proper position at the sewing station of the machine, an auxiliary working surface component is provided which is mounted upon the sewing machine outwardly from the conversion cover plate. This surface is slightly canted upward as it extends outwardly to aid in positioning the workpiece against the upwardly extending cover plate guide surface. The original stroke of the sewing machine is maintained through the utilization of a needle of a type wherein the eyelet is spaced quite closely to the tip as compared to a more conventional needle. Additionally, an edge guide may be installed inwardly of the sewing station of the machine to engage the outer periphery of the rim of the molded sole to thus position the stitching line or locus uniformly from that periphery. For molded sole structures having the rim extending from a bottom surface, an alignment guide, again installed inwardly of the sewing station may be provided which engages the rim to align it with the level of the elevated sewing surface prior to its advancement thereon.
In one aspect, the invention provides a method of converting a sewing machine having a flatbed sewing surface, a sewing station with given stroke, a needle, a lower disposed bobbin and sewing hook, compound feed components having a given extent of reciprocal travel including a reciprocal feed dog, a cover plate, an upper feed and a presser foot for sewing the rim of a molded sole of given rim to bottom thickness to an upper which comprises the steps of:
Providing a cover plate conversion assembly having a lower plate portion with a dog receiving slot, an edge guide having a guide surface extending upwardly and generally normally to the lower plate portion to an elevated sewing platform surface generally parallel to the lower plate portion and having a needle or receiving slot formed therein;
providing a conversion dog assembly having a workpiece advancing component configured for reciprocal movement within the dog receiving slot and a thread sequestering channel component adjacent to and extending upwardly from the advancing component to a needle receiving opening located for reciprocal movement adjacent the needle receiving slot of the conversion cover plate assembly;
removing the cover plate;
removing the feed dog;
installing the conversion feed dog assembly in place of the feed dog; and
installing the conversion cover plate assembly in place of the cover plate, the edge guide surface being located in the spaced adjacency with the thread sequestering channel component and the needle receiving opening being located adjacent the needle receiving slot.
Another feature and object of the invention is to provide a kit for converting a sewing machine of a variety having a flatbed sewing surface, a sewing station with a given stroke, a presser foot, a top feed mechanism, a needle, a lower disposed bobbin and sewing hook, a feed dog drive mechanism with a removably connected feed dog, and a removable cover plate, such conversion providing for carrying out the sewing together of first and second workpieces, the first workpiece having a thickness portion of at least about xc2xc inch between top and bottom surfaces and further having a rim extending outwardly from one of the top and bottom surfaces, the second workpiece having a peripherally disposed portion for sewing attachment with the rim. The kit comprises:
A conversion cover plate assembly configured for mounting in place of the removable cover plate, having a lower plate portion locatable in alignment with the flatbed sewing surface, having a feed dog workpiece advancement component receiving slot, an edge guide having a guide surface generally extending upwardly normally to the lower plate portion a distance corresponding with the first workpiece thickness portion to an elevated sewing surface configured for operation with the top feed mechanism and presser foot of the sewing machine and being generally parallel with the lower plate portion and including a needle receiving slot; and
a conversion feed dog assembly configured for mounting upon the feed dog drive mechanism in place of the removably connected feed dog, including the workpiece advancing component and a thread sequestering channel component adjacent to the workpiece advancing component and extending upwardly a distance generally corresponding with the guide surface distance to a needle receiving opening and located for operably associating the needle and the sewing hook of the sewing machine.
A further feature and object of the invention is to provide a sewing machine for stitching together first and second workpieces, the first workpiece have a thickness portion of at least about xc2xc inch between top and bottom surfaces and having a rim extending outwardly from one of the top and bottom surfaces, the second workpiece having a peripherally disposed portion for sewing attachment with the rim. The sewing machine comprises a flatbed defining a first work surface, an arm extending outwardly over the flatbed to a compound sewing mechanism including a compound reciprocating needle and top feed mechanism and a height adjustable presser foot. A bobbin and sewing hook are mounted for actuation below the first work surface for operational association of bobbin fed thread with needle carrying thread to define a sewing station. The cover plate assembly is provided having a lower plate portion at the first work surface with a feed dog workpiece advancing component receiving slot, an edge guide having a guide surface generally extending upwardly normally to the lower plate portion a distance corresponding with the first workpiece thickness portion to an elevated second work surface operable with the top feed mechanism and presser foot and which is generally parallel with the first work surface and includes a needle receiving slot. A feed dog assembly including the workpiece advancing component is provided, the latter component being extensible through the receiving slot of the cover plate assembly and a thread sequestering channel component is provide adjacent to the workpiece advancing component which extends upwardly to a needle receiving opening located for reciprocatory movement adjacent the needle receiving slot at the second working surface. A sewing drive mechanism is provided for carrying out the actuation of the needle, top feed mechanism, bobbin, sewing hook and feed dog assembly.
Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter. The invention, accordingly, comprises the method and apparatus possessing the construction, combination of elements, arrangement of parts and steps which are exemplified in the following detailed description.